oilman 0 Posted October 18, 2005 Viscosity Index Improvers. An oils viscosity will decrease as the engine temperature rises. Viscosity Index Improvers are added to reduce this thinning. They are a key addative in the production of multigrade oils. VI Improvers are heat sensitive long chain, high molecular weight polymers that minimise the viscosity loss of the oil at high temperatures. They work like springs, coiled at low temperatures and uncoiling at high temperatures. This makes the molecules larger (at high temps) which increases internal resistance within the thinning oil. They in effect "fight back" against the viscosity loss in the oil. "Shearing" The long chain molecules in VI Improvers are prone to "shearing" with use which reduces their ability to prevent the oil from losing viscosity. This "shearing" occurs when shear stress ruptures the long chain molecules and converts them to shorter, lower weight molecules. The shorter, lower weight molecules offer less resistance to flow and their ability to maintain viscosity is reduced. This shearing not only reduces the viscosity of the oil but can cause piston ring sticking (due to deposits), increased oil consumption and increased engine wear. Like basestock quality, VI Improvers also vary in quality. As with many items the more you pay, the better the finished article and more expensive, usually synthetic oils are likely to incorporate better VI improvers. All other things being equal the less VI improver an oil contains, the better it will stay in grade by resisting viscosity loss. Which oils require more VI Improvers? There are two scenarios where large amounts of these polymers are required as a rule. Firstly in "wide viscosity span" multigrades. By this I mean that the difference between the lower "W" number and the higher number is large for example 5w-50 (diff 45) and 10w-60 (diff 50) are what is termed as "wide viscosity span" oils. Narrow viscosity oils like 0w-30 (diff 30) or 5w-40 (diff 35) require far less VI Improvers and therefore are less prone to "shearing". Secondly, mineral and hydrocracked (petroleum synthetic oils) require more VI Improvers than proper PAO/Ester (Group IV or V) synthetic oils as they have a higher inherent VI to begin with, this is due to differences in the molecular straucture of the synthetic base oils compared to mineral oils It is a fact that many synthetics require significantly less VI Improver to work as a multigrade and are therefore less prone to viscosty loss by shearing. Cheers Simon Quote Share this post Link to post Share on other sites
Kevin Bacon 5 Posted October 18, 2005 :thumbleft: Great info! I must say, the Silkolene Pro S 10W/50 (ester) I bought from you is superb stuff. Consumption has halved and the engine is noticably smoother, aswell as quieter. It's also a funky purple/red colour which I guess is the ester? Quote Share this post Link to post Share on other sites
oilman 0 Posted October 18, 2005 It is a top oil and is no more expensive than Castrol RS or Mobil1. The red colour is a dye. Glad you like it, shame more haven't discovered its benefits ;) Cheers Simon Quote Share this post Link to post Share on other sites
Kevin Bacon 5 Posted October 18, 2005 A bit cheaper actually as Mobil and Castrol only give you 4L for £40, but Silkolene give you a more useful 5L for, what, £35 is it? I took advantage of you recent deal and bought 20L of the stuff :-) I think the reason not many people are taking the plunge is due to the cost. You can buy 15L of synta for the price of 5L of Silkolene but I personally felt an ageing VR6 could do with a 'wider viscosity span' oil, and it works ;-) Quote Share this post Link to post Share on other sites
oilman 0 Posted October 18, 2005 Synta is cheap because it's not in the same league but if the car is modded or used on track, Synta's not the oil, Pro S is. Cheers Simon Quote Share this post Link to post Share on other sites
Kevin Bacon 5 Posted October 18, 2005 Couldn't agree more. The bearings in my supercharger are £100 each (rated to 65,000 rpm) so they need synthetic really. Quote Share this post Link to post Share on other sites
STORM 2 0 Posted October 18, 2005 SO, oilman, what sort of deals are you doing on this lube? If I wanted to be adventurous and try it out? How does the price compare to Magnatec (currently using)? Quote Share this post Link to post Share on other sites
oilman 0 Posted October 18, 2005 Magnatec is a mineral oil, this is a proper synthetic. There is no comparison in quality I'm afraid. Prices are as follows: 5L £39.99 10L £69.99 20L £122.99 Cheers Simon Quote Share this post Link to post Share on other sites
The Leningrad Cowboy 0 Posted October 18, 2005 I'm not being funny, and working in the aeroengine industry, I am obviously interested in oils, especially those working across extremes of temperature for very high load applications, so this was great. :notworthy: But what brought on your (not particularly short) soliloquy? :scratch: :wink: Quote Share this post Link to post Share on other sites
Kevin Bacon 5 Posted October 18, 2005 But what brought on your (not particularly short) soliloquy? :scratch: :wink: It'll hopefully lead to a sale :lol: Quote Share this post Link to post Share on other sites
oilman 0 Posted October 18, 2005 I always post information that I think will be of interest to car owners from time to time. I have plenty more where that came from ;) I am a fan of synthetics (good ones) and of course sell them. Cheers Simon Quote Share this post Link to post Share on other sites
Tekara 0 Posted October 18, 2005 It'll hopefully lead to a sale :lol: All most worked for me, i think i will purchase some next month when the service is due. Quote Share this post Link to post Share on other sites
coullstar 0 Posted October 19, 2005 Tried some of the 15w-50 Mobil 1 this weekend on a trackday and it was great. Temp were only slightly higher than norm and consistent throughout the day. The car also appeared to use very little oil at all. Quote Share this post Link to post Share on other sites
DelMonty 0 Posted October 19, 2005 What oil would you recommend for a standard ageing VR? I currently use 10-40 Magnatec, which on the bottle states it's synthetic??? Quote Share this post Link to post Share on other sites
oilman 0 Posted October 19, 2005 What oil would you recommend for a standard ageing VR? I currently use 10-40 Magnatec, which on the bottle states it's synthetic??? The Magnatec 10w-40 is what they call a hydrocracked mineral oil, its still a mineral multigrade but of the purist form, they are allowed to legally call this synthetic, yet in the true sense of the word it is not. True synthetics are made from PAO base stocks made in a lab and designed for the purpose. For the VR, you can go for a good 5w-40 full synthetic or if the car is modded and used on the track then a good 10w-50/15w-50. CHeers. Quote Share this post Link to post Share on other sites
Jim 2 Posted October 19, 2005 Just out of sheer curiosity, do you do / reccomend an oil for VW PD Turbo Diesel engines? Quote Share this post Link to post Share on other sites
Kevin Bacon 5 Posted October 19, 2005 Don't you mean 'shear' curiousity Jim? :-) Quote Share this post Link to post Share on other sites
Jim 2 Posted October 19, 2005 Previous post deleted. I didn't get the joke Kev.. and made myself look silly ;) Quote Share this post Link to post Share on other sites
oilman 0 Posted October 19, 2005 Just out of sheer curiosity, do you do / reccomend an oil for VW PD Turbo Diesel engines? The PD engine requires a PD specific oil. We usually recommend this one as they do 15,000,000 litres factory fill with VAG per annum! http://www.opieoils.co.uk/TechSpecs/tit ... 05w_40.pdf Cheers Simon Quote Share this post Link to post Share on other sites
Kevin Bacon 5 Posted October 19, 2005 There you go Jim, you need to give your engine some good FUCHs mate. :-) Quote Share this post Link to post Share on other sites
Jim 2 Posted October 19, 2005 Thanks oilman :) Yes Kev.. seems like a good fuchs does wonders :) Quote Share this post Link to post Share on other sites
oilman 0 Posted October 19, 2005 Unfortunate name but German and the owners of Silkolene these days as well. Cheers Simon Quote Share this post Link to post Share on other sites
Jim 2 Posted October 19, 2005 S'ok.. my humour is squarely rooted in Beavis and Butthead territory. Ordinary people probably don't find it all that funny ;) Quote Share this post Link to post Share on other sites
Kevin Bacon 5 Posted October 19, 2005 It's my humour too :-) It's the same as SMEG fridges though...terrible name, top quality products ;-) Quote Share this post Link to post Share on other sites
Jim 2 Posted October 19, 2005 lol.. SMEG fridges and Nad stereo gear ;) Tee hee :D Quote Share this post Link to post Share on other sites
